The present invention relates to disk devices adapted to execute serial communication and a method of controlling the disk devices, and more specifically to a disk device which is suitable for a hard disk drive that is intended to reduce electric current required when initiating rotation of a spindle motor to rotate a disk, and a method of controlling the disk device.
Devices using various types of media such as optical disks and magnetic tapes are known as information recording and reproducing devices. Among them, hard disk drives (HDDs) have become popular as storage devices for computers to such an extent that they are one of the storage devices indispensable for today's computers. Further, not limited to computers, their application is widening more and more due to the superior characteristics with the advent of moving picture recording/reproducing devices, car navigation systems, removable memories for digital cameras and so on.
With disk devices represented by the HDDs, they are configured such that read/write operations of data are executed with a read/write head on a disk that is rotated at a high speed by a spindle motor. When a spindle motor drives a disk, the maximum driving current is applied to rotate the spindle motor during the start-up period. This produces problems in that power consumption during the start-up period is large and a noise level is high.
Taking the above into consideration, in patent document 1 (Japanese Patent Laid-open No. 2002-32952), for example, a start-up signal associated with the minimum level of the electric current required for starting up the spindle motor is applied to the driving unit of the spindle motor to increase the rotation speed of the spindle motor to the specified rotation speed. Then, when the specified rotation speed is reached, the signal is switched over to the one which keeps the rotation speed of the spindle motor lower than the specified start-up rotation speed, and thereafter, a feedback control is applied to the driving unit of the spindle motor to keep the rotation speed. With such an arrangement, start-up power consumption is reduced by starting up the spindle motor with the minimum required electric current, thus minimizing the starting power.
Meanwhile, as interfaces for transmitting data between superordinate equipment (hereinafter referred to as the “host”) and an HDD, such protocols as the Small Computer System Interface (SCSI), AT Attachment (ATA) interface and so on are generally used. In particular, the ATA interfaces are used in many computers in terms of improved interface functions and economical cost, and are also used as interfaces to storage devices of other types including optical disk storage devices. Due to requirements for improved recording density and performance of recording media, requirements for data transmission rate of the ATA interfaces are increasingly becoming more severe. In this connection, an ATA interface (Serial ATA) using serial transmission is proposed as a replacement of a conventional transmission system using a parallel transmission technology.
Standards for the Serial ATA are being formulated by the “Serial ATA Working Group”, and non-patent document 1 (“Serial ATA II: Extensions to Serial ATA 1.0 Specification” (Retrieved on Sep. 24, 2004), Internet <URL: http://www.serialata.org/collateral/index.shtml>) which was already released states the detailed specifications thereof.